An electret is a dielectric material with an embedded static electric charge and/or a dipole polarization. Electrets have high resistance, so their static electric charges and/or dipole orientations are quasi-permanent, i.e., their static electric charges and/or dipole orientations remain intact for time periods of up to hundreds of years. Because electrets have a static charge, they attract oppositely charged particles. This property can be exploited to remove oppositely charge particles that flow over or through a fibrous structure or thin film of electret material. The oppositely charged particles cling to the electret material until the filter becomes overloaded with particles, at which point the filter is cleaned manually or discarded and replaced.